1. Field of the Invention
The present invention relates generally to a substrate holder, and a system and method for cleaning and drying the substrate holder.
2. Description of Related Art
Japanese Patent Laid-Open No. 7-58074 discloses a conventional substrate holder for holding a substrate, e.g., a semiconductor wafer (which will be hereinafter referred to a wafer ), and a system for cleaning and drying the substrate holder. Referring to FIG. 14, such a substrate holder and such a system for cleaning and drying the substrate holder will be described below.
A substrate holder, e.g., a wafer chuck a, comprises a pair of holding members b which are arranged laterally symmetrical so as to face each other. The holding members b comprises: a pair of substantially U-shaped frame members e, which have horizontally extending base portions parallel to each other, and horizontal portions extending vertically and downwards from both ends of the base portions; upper and lower holding rods c and d which are supported on the lower portions of the frame members e so as to extend horizontally in parallel to each other; and a pair of shaft portions f projecting from one sides of the frame members e in longitudinal directions of the base portions. Furthermore, each of the upper and lower holding rods c and d has a plurality of holding groves g for holding wafers aligned with each other.
On the other hand, a system for cleaning and drying the wafer chuck a mainly comprises: a rectangular tubular cleaning container i which is open upwards and downwards; a dry gas supply means j provided on both sides of the upper portion in the cleaning container i; a cleaning solution supply means k provided below the dry gas supply means j. The dry gas supply means j has a plurality of nozzles (not shown) at regular intervals to inject a dry gas toward the upper holding rods c or the lower holding rods d. The cleaning solution supply means k has a plurality of injection nozzles (not shown) at regular intervals to inject a cleaning solution toward the upper holding rods c or the lower holding rods d.
With the above construction, the cleaning container i of the cleaning/drying system h for the wafer chuck a has is connected to a lifter means (not shown), by which the cleaning container i is movable vertically to be positioned so that the cleaning solution or the dry gas can be efficiently injected onto the upper holding rods c or the lower holding rods d.
The wafer chuck a and the cleaning/drying system therefor are positioned by the relative movement using the lifter means. After the cleaning solution is injected sequentially onto the upper holding rods c and the lower holding rods d to clean the wafer chuck a, the dry gas is injected to the upper holding rods c and the lower holding rods d to dry the wafer chuck a.
However, since the wafer chuck a is formed by assembling a plurality of members, if the size of the wafer increases, the composing members must be thickened to allow the holding members b to have sufficient strength, and the depth and size of the holding groves g must be excessive to maintain the wafers in stable state. Thus, there is a problem in that the total size of the wafer chuck a and the cleaning/drying system h is increased, and there are problems in that the draining of the cleaning solution on the wafer chuck a is bad and a relatively large quantity of cleaning solution remains in the holding groves g after cleaning. Moreover, since the dry gas is difficult to contact some regions of the upper holding rode c or the lower holding rods d even if the dry gas is injected toward the upper holding rods c or the lower holding rods d, there are problems in that the drying time increases, the quantity of the dry gas to be used increases, and the drying efficiency and throughput decrease.